PostgreSQL provides a large
number of functions and operators for the built-in data types.
Users can also define their own functions and operators, as
described in the Programmer's Guide. The
psql commands \df and \do can be used to
show the list of all actually available functions and operators,
respectively.

If you are concerned about portability then take note that
most of the functions and operators described in this chapter,
with the exception of the most trivial arithmetic and comparison
operators and some explicitly marked functions, are not specified
by the SQL standard. Some of
this extended functionality is present in other RDBMS products, and in many cases this
functionality is compatible and consistent between various
products.